According to trigonal height measurement principles and methods in plain and slight high terrain, measures an annexed leveling line respectively by means of trigonal height measurement and four-grade-leveling measurement, applies error propagation law to the system analysis and compares the measurement accuracy. The results show that the measuring accuracy of total station instrument is slightly higher than that of leveling instrument, and convenient for use, small restricted by topography and high work efficiency, so the trigonal height measurement can replace four-grade-leveling measurement.